1. Field of the Invention
The present invention relates to a pneumatic tire in which a crack is prevented from being generated in an inner peripheral surface of the tire, and to a producing method of the pneumatic tire.
2. Description of the Related Art
Conventionally, as a forming method of a rubber member such as an inner liner member, there is known a ribbon winding technique. According to the ribbon winding technique, as disclosed in a Japanese Patent Application Laid-open No. 2002-178415, a rubber ribbon made of unvulcanized rubber composite having small width and small thickness is wound along a circumferential direction a plurality of times and a rubber member having desired cross section shape can be formed. With this, the rubber member can easily be formed precisely as compared with a case in which a cut rubber extrudate is formed continuously in an annular shape.
When a pneumatic tire in which a tire cross section height is less than 110 mm and an aspect ratio (tire cross section height/tire cross section width) is small is formed using an inner liner member formed by the ribbon winding technique, however, it was found that the following inconvenience occurred. That is, in the case of the pneumatic tire whose tire cross section height is less than 110 mm, since large distortion is applied to a portion of the tire from the vicinity of an end of a belt layer to the tire cross section maximum width position during running, a crack is generated from a ribbon interface formed in the inner peripheral surface of the tire in that region, and the endurance of the tire is deteriorated.
A Japanese Patent Application Laid-open No. 2002-160508 discloses a pneumatic tire in which the inner liner member is formed by the ribbon winding technique, and an insulation rubber extending from the vicinity of an end of the belt layer to the tire cross section maximum width position is disposed between the inner liner member and a carcass ply. According to this pneumatic tire, however, since the ribbon interface is uniformly formed in the tire inner peripheral surface, the problem of a crack in the inner peripheral surface cannot be solved.
A Japanese Patent Application Laid-open No. 2002-79590 discloses a method for forming a tire inner peripheral surface of the inner liner member by a surface layer formed by winding a rubber ribbon whose width is less than 40 mm with a predetermined superposed width. According to this method, however, the relatively narrow rubber ribbon must be used, the ribbon interface is formed in the tire inner peripheral surface in a region where a large distortion is applied at the time of running in the pneumatic tire whose tire cross section height is less than 110 mm, and a crack can not be prevented from being generated in the inner peripheral surface.
A Japanese Patent Application Laid-open No. 2000-94542 discloses a method in which rubber ribbons are wound around both edges of an integrally extruded rubber extrudate to form an inner liner member. However, this method is for reducing the number of the winding steps of the rubber ribbon and enhancing the productivity by using the rubber extrudate, and this method is not for forming the inner liner member by the ribbon winding technique alone. To solve the problem of a crack on the inner peripheral surface, it is very important to reduce the ribbon interface in the tire inner peripheral surface in a region where a large distortion is applied during running, but none of the above producing methods disclose this point.